Single cell transcriptomics of of Abedinium reveals a new early-branching dinoflagellate lineage

Dinoflagellates possess many unique cellular characteristics with unresolved evolutionary histories including nuclei with greatly expanded genomes and chromatin packaged using histone-like proteins and dinoflagellate-viral nucleoproteins instead of histones, highly reduced mitochondrial genomes with extensive RNA editing, a mix of photosynthetic and cryptic secondary plastids, and tertiary plastids. Resolving the evolutionary origin of these traits requires understanding their ancestral states and early intermediates. Several deep-branching dinoflagellate lineages are good candidates for such reconstruction, however they tend to be delicate and environmentally sparse, so such analyses are not always simple. Here, we employ transcriptome sequencing from manually-isolated and microscopically documented cells to resolve the placement of two cells of one such genus, Abedinium, collected by ROV in deep waters off the coast of Monterey Bay. One cell corresponds to the only described species, ...